I don't see why the congregation would address this matter, they don't give us a reminder of all the laws we need to follow. They don't remind us that the tax deadline is coming up or to pay our car registration yearly. (I see expired license plates in the hall parking lot sometimes...) There must be a reason that they announce the selective service law specifically. I don't know what that reason is, though.
By the way, just in case anyone needs to know and doesn't, as we didn't realize back when it applied to "us", all males in the US 18 or older need to register for selective service, including US citizens, and all immigrants, including legal or illegal. We didn't realize they would want illegal immigrant males under 26 to register - had no idea, and it was a problem later when he was legal and applying for financial aid at school. And it came up when he applied for citizenship.
Another thing I'll add since no one seems to know, is that people in the US without an SSN can/should get an ITIN to pay their Federal Income Tax.
There's so many laws we can't possibly keep up with all of them. Who knew that in order to have a dog you need to have a dog license, in the city where we live. I thought you just buy a dog or someone gives it to you, and you get it vaccinated and fixed. Didn't know you need a license from the city. I would have unknowingly broken that law if I had a dog.
But we should do our best to be aware of and follow laws, of course. But say the government required a Real ID for everyone in the country in a month. Would that even be feasible? The people who need to give their fingerprints and report their address, hopefully the government let them know in a timely fashion and that the people have a way to actually do it. They probably know they need to fulfill all requirements in order to remain eligible to be able to stay in the US.
I'm just rambling here, don't take my words for concrete legal advice, do your own research