Script attribute that associates a transaction output with a group
Gid Gqty OP_GROUP => (nothing) ?
OP_GROUP is represented by the single byte 0xee.
Since OP_GROUP is an attribute, it MUST never appear in code. If it does appear, the script fails with an invalid opcode error.
The OP_GROUP clause MAY appear as the first element of P2PKH and P2SH scripts only. In this case this clause MUST be skipped. Execution should begin after the OP_GROUP opcode. If it subsequently appears, the script fails with an invalid opcode error.
The effect of groups on consensus operation is specified here.