I might be wrong, but I remember you can cover any song you want at a gig, since the venues already have a fee to pay to copyright associations or the like, so copyrighted material can be played live freely. This changes when it's an official release such as an album or a movie (as this case), then you have to pay royalties to be able to use that material. So, I think they have to pay if they want to release the movie containing Oasis songs, and that must be where this issue stems from.

As far as I know Liam has no ownership over the songs whatsoever.

Oasis as a band signed a record deal. I think McGee has said it was £40k. Oasis actually signed with SONY, and Creation had the UK rights (Creation were skint so borrowed money from SONY).

Oasis' members were paid a wage/salary by the record label, and got royalties. Noel signed a publishing deal for - I believe - £80,000.00 in 1994. I'm going off bits that I've read / heard here. 

Liam had no ownership over the material. And I'm guessing he will have signed away any rights he had to what he wanted to happen with the songs as soon as he signed the deal. It's guesswork but logic to suggest that. 

Oasis - the band - were owned by someone else as soon as they signed that deal, and then any subsequent deals down the line.

Noel Gallagher is the one who had the publishing deal and therefore he has the monetary rights to the songs (I'm guessing).

I mean, this is the same bloke that wished aids on people in the 90s, like. 

It's not a new thing that he's a twat - which he readily admits.

But him and Liam hate each other and neither party is innocent. Both are good at playing the victim card as well.

Also, this isn't the first time that Noel has done the dirty with legal proceedings. Him and Marcus absolutely rinsed Tony McCarroll.

The Voice most certainly pays the royalties for the covers. So yeah.

I'm sure it's just about royalties. Noel can't stop Liam releasing his own recordings of Oasis songs.

According to this site: www.makeitinmusic.com/licence-cover-song/

"...once a song has been commercially released by an artist, that artist's song may be re-recorded and released by anyone who chooses to do so.

This is only the case if the melody/lyric isn't substantially changed in your cover version, and you pay the proper fees/royalties directly to the song's copyright holders."

The publishing rights are separate to the ownership of the recording. Noel will have the publishing rights (so he gets royalties when someone covers his songs). But Liam & the band will own the actual recordings, so they will have a say in what happens to them (unless like Tony McCarroll they sold their rights for a lump sum.)

Covering a song live, recording a covered song and using a covered song in a film are 3 different things.

Live cover, as many has mentioned, usually the venues take care of it. 
To record a cover and release it, you'd need the mechanical license, and the rate is set by certain standard so the royalty due won't be a ridiculously high amount. note - it's only for the *audio* recording. 
To release a covered song in a video, a synchronisation licence is also needed to make it fully legit. And that's where the copyright owner can refuse to grant the permission if feeling the circumstance is not appropriate , or ask very high price. I think that's what they are playing with in this case. 

This is all about trying to hit Liam where it hurts by separating him from Oasis’s legacy. Blocking him based on ownership from a band he started and embodied.

Sad that One Love is still causing arguments. Chris Martin even thanked Noel for "giving your blessing and encouragement to play Don't Look Back In Anger and Live Forever", and now this

Unbelievable bitterness from the little fella.