Putter alteration advice | Golf Monthly

A summary of a response from the USGA Equipment Department in respect of decals. But IMO applies to anything which is 'stuck onto' a club

As a sticky label is considered to be an attachment it must conform to the interpretations for Rule 1.a and particularly interpretation 1.a(5) regarding External Attachments which requires attachments used as alignment aids to be semi-permanent in nature.

Whether a label is semi-permanent in nature depends on the nature of the adhesive used.

Consider the strength of the adhesive used, how easily the label can be removed and whether, generally, any outside agents such as alcohol or another adhesive solvent would be used to remove the label. If it takes some effort to peel away the label and\or a solvent to completely remove it, then it would be construed to be semi-permanent. If it is a peel and stick item that is very easily removed it of course would not.