"A well regulated militia being necessary to the security of a free State, the right of the People to keep and bear arms shall not be infringed."- US constitutional text.
Without the second their are no others
The second amendment is what gives US citizens the right to own and keep firearms. This has been put in place to keep the government in its place, otherwise known as keeping them from becoming tyrannical. In the act of common sense their are limits to how the amendment works. including gun ownership licences. this is to "ensure" that people who are convicted criminals or are not in a state of either physical or mental strength to comprehend the power of firearms and use them at times of self protection and protection of other citizens from those who seek to do harm to the innocent. of coarse all things are going to have a loophole. wile it may not be lawful to own a firearm as a convicted criminal their are black markets to get firearms. this is a problem but certified gun owners are getting the blame for unlawful gun use by criminals. wile most would count on the Govt. to help if their are crimes committed. they can not be their at a 5 second time margin, wile a firearm can be on your person for personal protection and keeping. furthermore owning a firearm dose not give you the right to commit murder even so if you kill a person who is attacking either you or someone else this is going to be taken to trial to see if their death was justified.
now that the basics have been covered lets delve a bit into an actual federal case regarding the second amendment. the case District of Columbia Vs. Heller 554 US 570. below is a link to were you can learn more In depth of the case.
to summarize this article, the trial was brought to the attention of the supreme court. whom decided that all firearms can stay loaded, but not including when in vehicles nor can they be loaded in a vehicle. when you ether disassemble or place a trigger lock on firearms it is impossible to fire the weapon hence the name "trigger lock". it prevents you from having quick access to your firearms and could put you in a solvable situation but due to those possible extra seconds that you do not have access. disassembling weapons is not easy nor is it a good idea especially if you plan to use the weapon to protect yourself. it was deemed unconstitutional due to it limiting the peoples right to firearms by a grate amount. their is considered a fine line when it comes to firearms and this was a case making that line far more pronounced and set in stone.