I think Liam and Noel own the brand Oasis, and both of them have the power to block something if they want. Liam said he gave his permission for the re-issues, even though he doesn't like re-issues that much.

Could be completely wrong but I'm sure in the early Beady Eye days Liam talked about having to dissolve ownership of the band with him, Andy and Gem receiving equal pay for their shares and Noel retaining overall ownership. Might have got the wrong end of the stick though.

It would tie in with Sony giving Noel overall control in 1994 and Liam being an employee despite founding the band.

I had a look and Noel and Liam both have the same amount of shares in Big Brother Recordings and both are "a person with significant control".

Sorry links are super long

Btw- this is the kind of interesting info we lose (or is at least hard to find) with streaming and digital. All of the above info is on the sleeves on the CD and other physical formats

I don't think there is anything Liam could have done different. To clarify the above I think this is how the ownership shakes out
There are publishing rights and Master rights.
For the first three albums
Noel (songwriter) owns the publishing rights and has a deal for his entire catalog with Sony atv. They split the profits, maybe 50/50, I'm not sure if that's the standard.
Oasis the band have a record deal with Creation/Sony. The band members are each paid royalties according to the contract.
Albums 3-6
Each songwriter has their own writing credits and publishing deal, you can see this on the copyrights on the album sleeves.
Record contract is with Big Brother Recordings Ltd owned by Liam and Noel but Noel might be the Ceo, not sure. Again band members will be paid according to contract.
Album 7 Publishing same as above, record deal through a joint deal of Big Brother/Sony BMG. This deal was reported to be for 3 new albums btw.

So for Liam to record and release his own songs in the movie, he would have permission from himself as the publisher but he would still need permission to use the Master rights by the record company, owned jointly with Noel.
     "Royalties generated for copyrighted music paired or ‘synced’ with visual media. Sync licenses allow the right to use copyrighted      music in films, television, commercials, video games, online streaming, advertisements, and any other type of visual media.

     Furthermore, a synchronization license does not include the right to use an existing recording with audiovisual media. A      licensee will also need a master use license before using copyrighted music with a new audiovisual project. This is an agreement between the master recording owner such as a record label and the person seeking permission to use the recording. Any use of protected music in an audiovisual project, whether it’s a full song or short sample, will need a master license as well as a sync license."
iconcollective.com/how-music-royalties-work/

Also it appears that Noel it trying to get the Master rights for the first three albums back but I'm not 100% if that what he was saying on the Seth Meyer show. The timing is right with this info that I found though, and he may have made it public to put his request on "record"
'Section 203 provides a chance for songwriters to terminate their assignments and recapture their copyrights. For works after January 1, 1978 (the year the 1976 Act went into effect) grants, assignments and licenses can be terminated during a five year window starting 35 years after such grant was made. For the termination to be effective a letter requesting that the copyrights revert to the songwriter must be sent no more than 10 years prior and no less than two years prior to the effective termination date. There are certain other formalities, such as recording a termination notice with the Copyright Office, for which you should contact an attorney experienced in recapture rights."

Here is an interesting book about record contracts that mentions Oasis a few times. I don't have it, just glanced through it on google books
books.google.com/books/about/Music_The_Business_7th_edition.html?id=XPI0DQAAQBAJ

For his solo stuff, it's extremely important that Liam get every bit of songwriting credit he deserves and get his publishing credit. This is what made Noel rich. Even if Liam is sharing it with the other guys, it's money that keeps coming in.
Also anyone out there in a band, if you contribute anything to a song, make SURE you get your co-writer credit!!