No, that's incorrect. 

1.  Such an "allowance" was made for persons such as politicians in order to attend such for political, govt reasons.

False.  This nonsense has been thoroughly debunked before.

Not only that, in this case, we're not talking about something that's formally non-Catholic (as explained above).

So I've been invited to an Indult wedding and mass, and I'm just looking for guidance/info to help make a decision on attending/not attending.
-I would consider the priests doubtful, as they are Novus Ordo priests, so reception of the Sacraments is a clear no.
-The groom is a friend, so I want to do what is charitable without transgressing any Church law/teaching.
Is there anything else I should consider, ie Church law on attending doubtful masses, active/passive participation?

Yes, you should consider that before attending the indult, that you first and foremost in no way question the legitimacy of the NOM. It is something to consider.......

Quattuor Abhinc Annos

Indult for Use of Roman Missal of 1962

"a) That it be made publicly clear beyond all ambiguity that such priests and their respective faithful in no way share the positions of those who call in question the legitimacy and doctrinal exactitude of the Roman Missal promulgated by Pope Paul VI in 1970."

Fr. Wathen:

"People should know that attending the Indult Mass represents a very serious compromise of their faith. Before a bishop allows the Traditional Latin Mass in one of his Novus Ordo churches, according to papal direction, he exacts this commitment: Those to whom the Mass is made available must give a verbal acceptance to the Second Vatican Council and to the new mass. Whether they know it or not, everyone who attends the Indult Mass makes the same implicit commitment. In the days of the Rome persecutions, a Catholic could escape martyrdom if he would burn the tiniest pinch of incense before one of the countless Roman gods. The commitment which the pope and bishops require is that pinch of incense."

Catholic moral theologians hold that one may attend, though not actively assist in non-Catholic worship.

  The indult is not non-catholic.  Therefore the canon law allowance doesn’t apply. 

What rubbish. Of course you can go to an Indult mass and wedding. For those falsely saying one couldn't, here is a refutation. If the Indult is a Catholic mass, one can always go to a Catholic mass, no issues. If it is supposedly a non-Catholic mass, either way one can still go, at least to assist passively at supposedly "non-Catholic" mass. In fact, the indult is Catholic, thus neither heretical nor schismatic, and one can go to said Mass and receive graces from it.

  The indult is not non-catholic.  Therefore the canon law allowance doesn’t apply.

You're not one for distinctions, are you?

1) Indult (= Tridentine Mass) is most certainly a Catholic rite (despite your broad equivocal use of the term "catholic")

2) Those who offer the Indult profess the Catholic faith.  While they may or may not adhere to various errors, they are most certainly not in the same category as a declared formally-schismatic "church", such as the Orthodox.  Even the most dogmatic SVs like Bishop Sanborn acknowledge this distinction, stating that for this reason they are not required to make abjurations before becoming Traditional Catholics.

While, objectivley speaking, the Conciliar Church is a (non-declared) non-Catholic institution, the Mass is Catholic and those who offer the Mass (and assist at it) do in fact profess Catholicism.

Now, one is permitted to passively attend even DECLARED non-Catholic funerals / weddings (all other considerations aside, such as risk of scandal or corruption of your faith -- and the risk of scandal is almost non-existent these days, since NO ONE construes attendance at a wedding or funeral as an endorsement of the religion under the auspices of which it's taking place).

Then, a fortiori, one may certainly attend the Indult Mass, and it is my opinion, even actively assist at it, since it's a Catholic Rite offered by those who profess to be Catholic (prescinding now from considerations regarding validity ... so, let's assume for the sake of argument that it's being offered by an elderly priest ordained before the New Rite(s) or by an ex-SSPX priest).

Then, a fortiori, one may certainly attend the Indult Mass, and it is my opinion, even actively assist at it, since it's a Catholic Rite offered by those who profess to be Catholic

You could attend an Indult mass if the priest was CERTAINLY validly ordained (i.e. ordained before 1970, or ordained in the sspx).

You could NOT attend an Indult mass for some random indult priest, as his orders are doubtful and the additional canon laws apply, which prohibit attendance at doubtful masses/sacraments, under penalty of grave sin.

“We cannot choose a less certain option, called by the moral theologians a simply probable manner of acting, that could place in doubt the validity of the sacraments, as we are sometimes obliged to do in other moral questions. If we were able to follow a less certain way of acting, we would run the risk of grave sacrilege and uncertainty concerning the sacraments, which would place the eternal salvation of souls in great jeopardy. Even the lax “probabilist” theologians admitted this principle with respect to baptism and holy orders, since the contrary opinion was condemned by Pope Innocent XI in 1679.

It is permissible in conferring sacraments to follow a probable opinion regarding the value of the sacrament, the safer opinion being abandoned.... Therefore, one should not make use of probable opinions only in conferring baptism, sacerdotal or episcopal orders."

(Proposition 1 condemned and prohibited by Innocent XI, Dz. 1151)

Consequently, it is forbidden to accept a likely or probably valid ordination for the subsequent conferring of sacraments. One must have the greatest possible moral certitude, as in other things necessary for eternal salvation. The faithful themselves understand this principle, and it really is a part of the “sensus Ecclesiae,” the spirit of the Church. They do not want to share modernist, liberal rites, and have an aversion to receiving the sacraments from priests ordained in such rites, for they cannot tolerate a doubt in such matters. It is for this reason that they turn to the superiors to guarantee validity.”

Anti indulters are borderline schismatic, especially if they are professing sedeplenists. remember one can commit schism in two ways (1) refusing to be subject to the Roman Pontiff (2) refusing communion with Catholics subjectto the Roman Pontiff, per St. Thomas. Prescinding now from considerations of #1, those who refuse communion with Indult Catholics word for word contradict and fall under #2, i.e. they refuse communion with Catholics subject to the Pope. Clearly erroneous and proximate to schism.

Even some of the most dogmatic SVs would permit passive attendance (for funerals/weddings, etc.) ... and, as mentioned, Bishop Sanborn stated that NONE of even the most hard-core SVs require abjurations for people coming over from the Conciliar Church to Traditional Catholicism, since they realize that it's not a formally-declared schismatic body like, say, the Orthodox.  It's kind of in a Limbo state between Catholicism and being non-Catholic.

I mean, I could be at a Catholic Unversity where we'd be studying non-Catholic religions (for legitimate purposes), and could show up at and attend some ceremony of theirs simply to observe it and take notes.  There can be various legitimate reason just to be "present", like a fly on the wall, provided that you're not actively participating in whatever they're doing.

Sure, this could apply to non-catholic services.  As an isolated incident.


But it would not apply to the Indult because a) it's a catholic rite, b) one is not there as some random person, as a one-time action of investigation.

People who would go to an Indult mass for the bride/groom or a funeral are a) giving scandal, b) there's no "grave reason" to be there, c) are not there as a one-time action.

What is the "grave reason" to go to an Indult mass?  So you don't "offend" somebody?  Sorry, that's not allowed by canon law.

Even some of the most dogmatic SVs would permit passive attendance (for funerals/weddings, etc.)

Who cares?  Even some of the most dogmatic SV's think non-catholics can be saved.  They obviously think Indulters can be saved, too.  And so can new mass'ers.  The only people who *can't* be saved are Trads who go to 'una cuм' masses...which makes no sense...but that's another topic. 

The point being, dogmatic SVs aren't 100% right on everything.