Again poland could if spotting a foreign drone within polish borders would have to surveil it and decide if its an actual viable threat, and then shoot it down. if not a threat or in international space or other things then poland can just watch and report and gather more evidence to strengthen viability for future incursions to be probable threats
Yes that is correct. They will assess the threat and based on previous experiences,
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Regarding Israel, I agree that they cannot legally attack a foreign country without a declaration of war.
The real solutions are the agreements for disarmament from all sides, but that is currently impossible.
declarations of war are towards the country that the strike happened in. however there are other laws that allow "pre-emptive strikes" to take out specific targets without it leading or needing a declaration of war, if such strike as significant military defence strategy and mitigating risk/loss of the host country housing the military threat that was targeted. can be deemed as a pre-emptive strike and not lead to war. especially when the intended targets of the strike were not that of citizens nor military nor government of the host country the targets hide in