What can we do to ensure that the sale of weapons to dictatorial countries which they use against their own...

Question

... people will become illegal?

Answer 1

Stop america taking sides and giving weapons.

Answer 2

The  main nation complicit in this affair is the US.  Look at all the tin-pot regime's they have backed:  many in the Americas, Saddam Hussein, the Shah of Iran.

Remember the fickle history of the US in world affairs: 'today's friend is my future enemy, and we Americans have the right to sell arms to whomever we wish'.