if the defender change his status from war to right of way the attacker can cancel it if go again at his status and change it to war again its a good trick for the defender if the enemy send his army but he is ofline

Sorry, but it doesn't work that way @I.N.T.R.U.D.E.R - only if the other player accepts the "right of way" will it actually switch to it, so you cannot use it to make an enemy automatically stop attacking.
Right of way is actually "Peace+" so to speak. Some players use it as a trick, but if you accept right of way during hostilities, they will of course stop.
Factually you are now granting your erstwhile enemy the ability to use your roads and even airbases. He will abuse this and then break the ROW and continue fighting ... most probably.

As I've said a hundred times before: be careful whom you grant R.O.W. (to quote a famous admiral: "It's a trap!")
We are not changing it because we allow players to play deceitfully an unfairly within the game rules - not everyone is an honorable enemy after all and some players indulge in this type of game play, claiming it as a "ruse de guerre".

//G

i know you must accept the right of way if the enemy makes you an offer. but if i am the defender for example and the enemy attacking and i change my status from war to right of way at diplomacy panel the enemy troops moving at theyr targets but they dont conquer the land that happened to me also in a game but i was online and i change it to war again

Sorry but I just tested exactly this scenario again and it is working as intended - meaning the AI or player who does not accept the offered ROW simply conquers as before. Only if he accepts does he of course stop.
Anything else is a bug - but not apparent or already fixed.