Need to formally give notice of withdrawal or whatever the process it.
Internal decisions/processes do not count
See also:
Internal decisions/processes do not count
@MalachiteEagle We need to wait for a formal withdrawal, which must be done by this handsome man:

@skibidist No, this is formally giving notice on withdrawal. This is being done across multiple governments simultanously. This is not an internal decision.
@MalachiteEagle No, that is not correct. This is a recommendation, as the article says
recommend withdrawing from the Ottawa Convention
Only the president can make the decision in Poland - he very likely will, but no formal process has been initiated by this announcement
@MalachiteEagle something like that, a statement of intent I guess .. I think the purpose was to make the shared declaration since the actual process will be different in each country