Skills claiming they cannot be used even though they can

Requirements to equipped items / skill gems only check the currently active attributes .

Attributes when using Weapon 1 : 50 INT
Attributes when using Weapon 2 : 150 INT

Affecting a 100 INT skill gem to Weapon 2 works fine , but as soon as you switch back to Weapon 1 this skill will be marked as invalid even though it is binded to Weapon 2 only .