I need an ASM i-rule that drops the connection upon the occurrence of a violation.

Sometimes the handoffs between the primary proxy and plugin architecture clients like ASM are obscure. You might need to set a variable in the ASM event and then evaluate in the HTTP_RESPONSE_RELEASE event. Try something like this:

when ASM_REQUEST_VIOLATION {
    set req_violation 1
}
when HTTP_RESPONSE_RELEASE {
    if { [info exists req_violation] } {
        drop
    }
}