Is Denying A Pto Request Considered Retaliation?

Hello!

I am a union represented RN in USA, residing in the state of Oregon. We are currently on an indefinite strike which started on 1/10/25.

I requested PTO several months ago in adherence to the guidelines outlined in my company's PTO policy. Under normal circumstances, this PTO request would undoubtedly be approved (I work in a clinic with one other RN, I have the most seniority and no other RN's have requested time off during the dates I have requested off)

After the strike began, my PTO request was then denied, with the stated reason "unable to approve at this time".

Assuming the strike ends prior to my requested dates, I have two questions before I go to the union with my concern:

1: Does my employer have to provide a clear and legitimate business reason for denying a request for paid time off?

2: Is denying a PTO request that would normally be approved under normal circumstances considered relation for participating in the strike?

I appreciate any feedback you can provide!

(further details: The PTO request deadline for the schedule period of Feb 24-Mar22 was on Jan 12th. My request was submitted in mid 2024, prior to the 1/12/25 deadline. The schedule post date is 1/29/25.)