If any country is going to land on our shores in anger, you can be sure that it was never international laws which could have stopped them!!
International laws don't prevent breaches through 'someone' enforcing them against states who break them. How could that work? These are sovereign states with their own armies.
Allegiances like NATO might, since each member has committed to going to the defence of any other NATO state at their request if they're invaded. And everyone knows that to be the case, so are discouraged from attacking.
Our nuclear deterrent might help too.
But not international laws!
They were created after WW2 finished, as a way for countries to codify the best practice they would all like to live by. And to give support to countries to abide by them/aspire towards them. And diplomatic means for discussion and negotiations where there's conflict between states - with clarity about what had been agreed 'in principle' - which could hopefully make wars less likely. That's really all.