All weapons used by the LDF are known to be used/taken from JSDF stockpiles as "donated" by local governments to defend libraries against the Media Betterment Act (MBA).
Minebea P9
The main sidearm of the LDF is the Minebea P9, a licensed copy of the SIG-Sauer P220 manufactured by Minebea and Shin Chuo Kogo KK. Kasahara (Nana Eikura) and Captain Genda (Jun Hashimoto) wield these weapons. Various LDF soldiers are seen with the P9 in their holsters.
Minebea M-9
The primary submachine gun of the LDF is the Minebea M-9, a copy of the Mini Uzi manufactured under license by Minebea.
Micro Uzi (Mocked-up as Minebea M-9)
For some reason, not enough Minebea M-9s were available for the LDF extras during production. The Micro Uzi was used as a stand in for the Minebea M-9 for some scenes. The folding stock appears to have been removed
Howa Type 64
The Howa Type 64 is used as a training rifle for all recruits prior to indoctrination into the LDF, most noticeably Tezuka (Sota Fukushi) and Kasahara
Behind The Scenes
Howa Type 89
The Howa Type 89 is the main assault rifle of the LDF.
Remington M24 Sniper Weapon System
The M24 Sniper Weapon System is the LDF's standard sniper rifle, and is equipped with a Harris bipod. It's possible that these weapons are airsoft replicas, since none are seen ejecting brass, and the muzzle flashes appear to be post-production CGI
M84 Stun Grenade
Dojo throws an M84 stun grenade into a room during a hostage rescue. It's surprising that the LDF never employ stun grenades during their battles with the MBC, despite their fighting doctrine and less-than-lethal nature.
Media Betterment Committee
Heckler & Koch MP5A4
One of two submachine guns of the MBC is the Heckler & Koch MP5A4. The MP5A4 supplements the more common MP5A5 fielded by the MBC. These weapons are occasionally seen outfitted with Surefire 628 forearms and, at least one is equipped with a tri-rail forend, though it doesn't have any attachments mounted to it.
Heckler & Koch MP5A5
The most common weapon seen in the hands of the MBC. Many are equipped with the Surefire 628 forearms and flashlights, and some have receiver-mounted rails, though none mount optics with the exception of AimPoint Comp M2's from a lecture.
Bakushukai Militants
Norinco Type 56
At least one Bakushukai Militant is seen wielding a Norinco Type 56 in the film's intro.
M2 Flamethrower
One of the Bakushukai Militants uses an M2 Flamethrower to burn down the Hino Library.