The right to bear arms was included in our Bill of Rights. The Bill of Rights was the first part of our Constitution to be written, and guarantees all citizens the right to own a gun, the right to worship as we please, and the right to the pursuit of happiness. Lots of other stuff in there...but rights are important! Especially when you LOSE them.
The Brits may only own guns if they have been grandfathered into various families who owned them before the UK outlawed gun ownership, if I am not mistaken. I think I saw something about it on Midsomer Murders on television.
Guns were used in the fledging United States by our Militia, to protect us from tyranny. And that right is precious to Americans because if our own government is ever led by a tyrant, our people enjoy believing that they could rebel against such tyranny.
Now, Biden likes to threaten the gun owners of Tennessee and other rural areas, who don't like tyranny, as our forefathers did not, and has said publicly that their guns would do absolutely no good during a carpet bombing by F15's, and mocked them...stating that THEY don't have F15's.
Guns are also used to hunt deer and elk, wild geese, and wild turkeys, and partridges. There are a lot of people here who rely on hunting for their meat consumption, ESPECIALLLY in Alaska. Some people there would starve if they couldn't hunt.
Now, to answer your question, (and sorry there was so much roundaboutation), Trump is not legally able to change our gun laws.
Because it is a basic right included in the Bill of Rights, a Constitutional Convention would have to be convened in order to change the Constitution.