ASM httpclass to local policy

You do not need to define a default ASM policy. You only need to define a default ASM action which could be "ASM Disable".

Use the lp_sample for your reference.

action_default If HTTP path match is false, request will receive TCP/RST packet from F5 in response

action_conditional1 If HTTP path match is true (/parentpath/subpath/path1 or /parentpath/subpath/anotherpath), F5 will enable ASM security policy sp_securitypolicy1

action_conditional2 If HTTP path match is true (/parentpath/path2 or /parentpath/anotherpath2), F5 will enable ASM security policy sp_securitypolicy2

ltm policy /Common/lp_sample {
    controls { asm forwarding }
    requires { http }
    rules {
        action_conditional1 {
            actions {
                0 {
                    asm
                    enable
                    policy /Common/sp_securitypolicy1
                }
            }
            conditions {
                0 {
                    http-uri
                    path
                    values { /parentpath/subpath/path1 /parentpath/subpath/anotherpath }
                }
            }
            ordinal 2
        }
        action_conditional2 {
            actions {
                0 {
                    asm
                    enable
                    policy /Common/sp_securitypolicy2
                }
            }
            conditions {
                0 {
                    http-uri
                    path
                    values { /parentpath/path2 /parentpath/anotherpath2 }
                }
            }
            ordinal 3
        }
        action_default {
            actions {
                0 {
                    forward
                    reset
                }
                1 {
                    asm
                    disable
                }
            }
            ordinal 1
        }
    }
    strategy /Common/best-match
}