I asked the USGA on this also, wondered if you had come across this situation.

Quote:

-I am playing a casual round of stroke play golf with a fellow competitor from my club. -On the green we are both putting for birdie from 15 feet away and I am away by an inch or so, but approximately 2 feet away from his ball. -His ball marker and line interfere with my stance so that I cannot take a putting stance without stepping on his marker or line. Of course, he does not offer to putt first in good spirit. How can I proceed, and what rules should I observe in this situation?

Good question! I do not see an easy solution but I can tell you what I have done.

If stepping on his marker causes you a problem, have him move it, just like one would move the marker to one side or the other for a putt. If the marker is not a problem and the other player is okay with it, just stand on his marker.

Once you make him aware that you are going to be standing on his line and he does not offer to putt first, proceed with standing on his line. Do not change the way you stand or putt one iota. The other player understood what was going to occur and gave you permission. So I just proceed and ignore the fact that I may be standing where his ball lies or on his line.

Yea, I thought that since standing on his line was the issue, it wouldn't have mattered if he marked his ball or not. he wouldn't appreciate me leaving marks or indentations that would affect his putt.

I don't think there is any rule about standing or not standing on someone's line. Obviously there is an etiquette issue, but if you've offered to let him putt first, and he has declined, then all bets are off.

I hope that is the same answer that the USGA gives me. I knew he was trying to get a line from my putt, which I missed and he made. I expect that it's on me because I struggled to take a compact stance so as not to disturb his line, in doing so completely hosed the putt.

Rule 16-1 e. Standing Astride or on Line of Putt

The player must not make a stroke on the putting green from a stance astride, or with either foot touching, the line of putt or an extension of that line behind the ball.

Exception: There is no penalty if the stance is inadvertently taken on or astride the line of putt (or an extension of that line behind the ball) or is taken to avoid standing on another player's line of putt or prospective line of putt.

Also: I cannot find it, but somewhere it mentions something about location of his marker or ball in your path or similar... I think it might be under match play rules though.

@TeT... I believe that rule is in regard to your own putting line, not another player's.

TeT wrote:

The player must not make a stroke on the putting green from a stance astride, or with either foot touching, the line of putt or an extension of that line behind the ball.

Note it is "the ball", not "a ball". This rule is all about your own line of putt, not the line from another player.

Quote:

Also: I cannot find it, but somewhere it mentions something about location of his marker or ball in your path or similar... I think it might be under match play rules though.

Not that I know of.

Anyway, Decision 16-1a/13 explicitly allows you to stand on other's line of play line:

Decision 16-1a/13 wrote:

A There is no penalty. Rule 1-2 is not applicable. In equity (Rule 1-4), the player may have the line of putt restored to its original condition. The player is entitled to the lie and line of putt he had when his ball came to rest. The line of putt may be restored by anyone. (further explanation removed for brevity)

I just copy / pasted the rule from USGA site.