required receivers of imported select-fire rifles to be Cut in Half?
From potentially fuzzy memory, that goes back to '69 or '70 or so, as an add-on to other Import Restrictions after GCA '68 invented the "sporting purposes" notion, and around the One and Only NFA Amnesty.
It's in the CFR (again, if memory serves correctly) which means it was entirely via BATFE (not needing any sort of POTUS signature nor approval). Imported Select-fire receivers are where we get the "once a machine gun, always a machine gun" rhetoric, which actually
only applies to imports (not that said distinction much limits ATFTE enforcement policies).
Obama was up against solid Congressional support for those bills, politically, he
had to sign them, as Congress would have overturned his Veto. Even so, both of those were flawed as delivered. Many National 'properties' were not included in the carry change--so Refuges, Conservation Areas, and places out of the Parks system were excluded from consideration. Even the NPs were allowed to post "sensitive areas" and you did not know until you saw the posting.
The AmTrak deal did not (really) last beyond 9/11, and you had to rely on FOPA in case the train rolled through a prohibited area (like NJ, MD, MA, CT, NYS, or the like), so the bill wound up being so milquetoast as to be meaningless.
FOPA was both fish and fowl (or foul, if you will). It was politically necessary to start the tide turning, and to show WRC that the new GOP Congress was to be reckoned with. It was a tad dumb in that it mostly just got rid of things that were being poorly administered anyway. The "travel between States" was the weakest water possible--but was still better than
status quo ante. The Hughes Amendment was meant to be a "poison pill" to keep the GOP lawmakers from voting in favor, but they ignored it for the "larger win" such as it was. This was reflected in how it was rammed in, possibly 5 minutes past deadline, to endure the poison pill remained no matter what.
Now, I suppose a case can be made that Andrew Johnson signing the 14th Amendment in 1866 did as much for ensuring national gun rights as any other POTUS.
Now, TR might get a nod for signing the Dick Act, aka The Militia Act of 1903, which allowed the Militia for be both the 10 USC National Guard and the repealing of the Militia Acts of 1795, with their mandatory training requirement and the like. Which, it can be argued, better reflected James Madison's "Who are the Militia? They are the whole of the people."