Generally, as I understand it, "standing" means you will/have been directly affected by the party that you are trying to sue -- in this case the government.
Trying to sue the govt. is difficult. If you don't have standing you could sue the govt for, say, infringing on your second amendment rights -- when you don't own any guns. You do it merely because you're offended the govt. is violating the constitution.
If that were possible then you could almost sue the government for anything.
IF you want to be a test case for some say, 2A issue, like challenging the NFA of '34 say, then obtain a NFA weapon without the tax stamp, allow yourself to be arrested, and then fight it out in court -- this way you will have standing and if you are REALLY LUCKY maybe SCOTUS will actually take your case -- AFTER you've spent $$$$ out the wazoo on lawyers.
But say I try to sue for violating the 2A by way of the NFA. I don't own any such weapons, I've never been arrested for violating it and never been hurt by it, therefor my case would be dismissed due to lack of standing.
Yea it sort of puts a brake on the idea of dealing with the NFA through lawsuit. OTOH the govt. would argue everyone and their brother would swamp the courts with bogus lawsuits if you didn't need standing to sue.
Has Rand Paul been hurt by NSA surveillance? I don't think so, from THAT point of view his case will be dismissed.
But as a senator....perhaps THAT could be said to be standing. I dunno how it works with the entitled classes .....