There are EA bylaws and any that don't comply are illegal:
You may not use a keepnet: -
(i) with any knotted meshes or meshes of metallic material; or
(ii) having any holes in the mesh larger than 25mm internal circumference; or
(iii) of less than 2.0 metres in length; or
(iv) with supporting rings or frames greater than 40cm apart (excluding the distance from the top frame to the first supporting ring or frame) or less than 120cm in circumference
You may not use a keepnet: -
(i) with any knotted meshes or meshes of metallic material; or
(ii) having any holes in the mesh larger than 25mm internal circumference; or
(iii) of less than 2.0 metres in length; or
(iv) with supporting rings or frames greater than 40cm apart (excluding the distance from the top frame to the first supporting ring or frame) or less than 120cm in circumference