One who is a non-Catholic, "in the process of conversion", has as much authority as anyone else to teach Catholics, in this time of extraordinary crisis, what the Church teaches.
Did I read that correctly???
And the CatholicMonarchist (NonCatholicMonarchist seems more appropriate) evidently believes that he taught us "from the very sources of the Church" that the Church has the authority to "temporarily halt Mass", and disobeying such a command is "grave matter".
What extraordinary pride.

Catholic Monarchist, you are one prideful pup. 

The decision to close each diocese has been made by each individual bishop, of each particular diocese, of each particular country, of each particular continent.  It has not come "from the pope" and these decisions were not made "in full communion with the pope".  Your facts, and as such, your conclusions, are completely wrong.

Edit:

True, but such directives and guidances are typically given from the Bishop of Rome in situations such as this.

You do have a point here that's been lost.  Whether or not the secular authority has any right to restrict Mass attendance, the hierarchy most certainly does.  One can argue argue about whether they should have done so, but one cannot, short of being a sedevacantist who considers them illegitimate, dispute that they have this right.

I can only speak of here in the US, but from what I've heard, the Bishops have suspended "public masses", not private ones.  Some liberal bishops may have cancelled everything.  ?
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Now, I'm not sure if the Pope himself forbade Mass attendance around the world, but I'm sure that he backs the decisions of the local episcopate.  So, since the U.S. bishops have shut down Masses, those who do not consider these illegitimate are in fact bound by their decree.

The pope has not ruled unilaterally, that ALL worldwide masses be stopped.  Even one of the priests in Italy back in April said that private masses aren't forbidden, only public ones.  He told his congregation (wink, wink) what time he was having his private masses.

In many states, such as here in Ohio, the directive is merely that there not be groups of more than 10.  So what if the SSPX (and others) assigned 15-minute timeslots for groups of 10 at a time (spread out by at least 6 feet along the Communion rail) to receive Holy Communion.  In an 8 hour day, 320 people could receive Holy Communion, and most Traditional chapels don't have anywhere near that many people.  Then also make some arrangements for people who wish to go to Confession beforehand.  I'm not seeing the SSPX make that extra effort to find creative ways to get the Sacraments to people.

I do know that some sspx chapels are having outdoor confessions, multiple masses, etc.  A few weeks ago, when the covid-craziness was higher, they didn't have masses, but still had confessions and adoration, with distancing and scheduling of people at certain times.  I don't know if this was at all their chapels, but I've heard similar stories from different states.
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To be fair to the sspx (as much as I criticize them), it takes quite a lot of time, energy and organization to come up with all these new logistics, on the fly, with such an out-of-the-blue situation arises like we're facing.  At least from what I'm hearing, some of their priests are making quite a heroic effort.  God bless them.
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The novus ordo "bishops", on the other hand, are making no efforts (and the blame should be placed squarely on the bishops).  Some of the novus ordo priests are holding drive-up benedictions, with confessions, but I hear no approval or congratulations from the bishops on these efforts.  It's all coming from priests. 
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Yet, there are still some new-priests that are doing nothing, out of "obedience".  One of my relatives emailed their local diocese priest and asked them if they could help organize confessions, or drive-thru benedictions or scheduled adoration.  The priest said he had to "obey" the bishop and couldn't do anything.  At least he apologized. 
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Both of these priests are under the same bishop, so you can see which priests really care about the Faith and which don't.

The diocese decisions in the US were made by EACH bishop in EACH diocese.  The pope did NOT close diocesan masses in the US.  

Yes. I realize that. Please see edit above.

The Pope and all of the Bishops in full communion with the Pope and by extension all of the Priests under the authority of said Bishops told us to stop attending Mass for the time being.

Just admit this is 100% wrong and we'll move on.  Do you have the humility to do so? 

The diocese decisions in the US were made by EACH bishop in EACH diocese.  The pope did NOT close diocesan masses in the US. 

The federally-funded USCCB basically did.

Firstly, a directive is not a guidance.  2 completely different things; opposites really.  The point is, you said the pope "in communion with" the bishops, stopped worldwide masses.  You are dead wrong.

A directive is an instruction for the management of operations; an official or authoritative instruction.

A guidance advice or information aimed at resolving a problem or difficulty, especially as given by someone in authority.
Via Oxford Dictionary.

You do see the overlap, no?

As to your point, that is not what I said. I said it was a directive from the Church. The beginning of my post was meant to illustrate what the authority of "The Church" consists of.