Scrumhalves can be the bane of referees' lives. Watch them at tackles, hands in the air in indignant appeal when they should be picking up the ball and passing it. They are, it seems, part of a team's machinery to work on the referee, presumably to get favours for their side. Here we have a referee dealing with a talkative scrumhalf.

When Saracens played London Irish, the Exiles were right on the Saracens line when the referee blew his whistle and penalised Paul Hodgson, the London Irish scrumhalf, for 'screaming at me'. That ended the attack all right.

In this incident, there is a maul with Benetton Treviso in possession. The maul collapses and the referee blows his whistle.

He immediately calls Tobie Botes, the Benetton Treviso scrumhalf to one side and then calls his captain, Antonio Pavanello. Quickly, clearly the referee explains to Pavanello why, in accordance with the Laws of the Game, the scrum is awarded to Munster.

Then he turns to Botes, introduces himself and warns him that any more shouting from Botes will mean a penalty against Benetton Treviso.

In all that the referee says he is succinct and clearly intending to carry out his warning. There is no doubt about it.

Has a referee the right to penalise a scrumhalf who shouts at him?

Law 10.4 (s) All players must respect the authority of the referee. They must not dispute the referee’s decisions. They must stop playing at once when the referee blows the whistle except at a kick-off or at a penalty kick following admonishment, temporary suspension, or send-off.
Sanction: Penalty kick

Also:

Law 10 DEFINITIONS
Foul play is anything a player does within the playing enclosure that is against the letter and spirit of the Laws of the Game. It includes obstruction, unfair play, repeated infringements, dangerous play and misconduct which is prejudicial to the Game.

Law 10.4 (m) Acts contrary to good sportsmanship. A player must not do anything that is against the spirit of good sportsmanship in the playing enclosure.
Sanction: Penalty kick

The referee is well within his right to act against any player who shouts at him. Apart from the manners of the thing, there is also the danger of giving the impression of yielding to pressure. It would be good if this sort of sanction could also be applied to 'medics' next to the touchline who shout 'advice' to referees.

The referee in this case is wonderfully articulate. The only danger to guard against is using the tongue to humiliate the player.