Help with papal letter passage

I am struggling with this passage in a papal letter granting a publication privilege to someone:

Nos enim quicquid secus super his a quoquam quavis auctoritate scienter vel ignoranter > attentari contigerit > irritum et inane dicta auctoritate decernimus

The bolded stuff in particular escapes me. So far, I have:

Moreover, we decree by the said authority that anything that differs from this [attentari contegerit] otherwise concerning these things by anyone on any authority [to be] without effect and vain

I just do not get how there is an infinitive combined with a finite verb in this context, especially since the finite verb does not appear to be governing the infinitive.

The phrase appears in other documents, but I cannot find any translations.

Also, the privilege does have some grammatical mistakes, so if upon reading you also feel like it seems off grammatically, that would still be helpful as confirmation for me.

Thanks!

As I see it: “whatever (quicquid) may happen (contigerit) to be attempted (attentari)”.

Thanks! I am more used to contigerit taking a subjunctive noun clause than an accusative and infinitive, so I was thrown off!