What's the most effective way to handle relatives who invite themselves over to your home frequently?  Particulary intrusive people who won't take no for an answer?

Be a good example in the things you do and discuss -- especially if they aren't Catholic.

I'm the OP--please don't tell me to be nice to them.  It's gone beyond that.   They are interferring in my marriage and homelife to point of separation from spouse.  

Please someone with some REAL LIFE experience offer some advice.  

You need to speak to your spouse first. Tell her that you love her very much, that you know she loves her family, but for right now she must remember that your marriage must come first and they need to stop visiting for a while while you work things out. It is important that you don't say bad or angry things about them to her (even if they're true); they are her family, after all. She might be reminded gently that though they remain important to her, and so to you as well, that she has sworn to put you above all others. (Above all others does not mean she has to cut all others out of her life!) Whatever you do, don't make her feel like she has to choose between you and her family. If you can not find a way to make peace or at least truce with the in-laws, then your marriage will not be happy. You might try "holidays only, for the next year" if you think you need time away from them. Try not to make restrictions against them that you wouldn't use against your own family, that would just breed deep resentment in all parties. You might also try removing yourself from the picture while they are visiting as much as possible. "Nice to see you, was just on my way out."  or "Hi, I have some studying-reading-work-important calls- etc... I'll be busy in the other room for awhile."

Simply tell them that your family needs more time free of disturbance from guests, for the peace and harmony of the household.

Just say:

I'm sorry, but we can't have any guests right now.  

If someone calls you and you are busy, how do you respond?

I'm the OP--please don't tell me to be nice to them.  It's gone beyond that.   They are interferring in my marriage and homelife to point of separation from spouse.  

Please someone with some REAL LIFE experience offer some advice.  

Follow your husband's lead.  He's the boss.  And stop threatening separation.

meddlesome grandparents can be a huge problem, they have to be put in their place.

Particularly when they are hostile to the husband and father.

Is this the OP?

I agree with Moderator that open confrontation is the only answer at this point, specially with people with no manners and no shame. If your children's souls are in jeopardy, for example, you need to make sure this people is avoided in your home at all costs. No need to be rude or compromise your manners, just concise and determined.

"Protect yourself from other people's bad manners by a conspicuous display of your own good ones"

"Rudeness is the weak man’s imitation of strength."