HH,
A pig must be tagged each time it
moves from one holding to another, unless it is under 1 yr of age when it can move on a temporary mark, except to slaughter or market or show. It is also illegal to remove a tag that has been applied.
So your friend is right, and for you in Scotland (the rules are similar in England)
comes under The Pigs (Records, Identification and Movement) (Scotland) Order 2011
http://www.legislation.gov.uk/ssi/2011/327/contents/madeand in particular Article 7
(1) No person may move a pig off a holding unless it has—
(a) an eartag with the letters “UK” followed by the herdmark which identifies the holding from which it is being moved;
(b) a tattoo showing that herdmark (with or without the letters “UK”); or
(c) a slapmark showing a unique individual identifier being—
(i) the herdmark which identifies the holding of departure; or
(ii) an alpha numeric identifier allocated to the keeper by one of the marketing or processing groups(1).
Article 8 give the under 1 yr...
8. (1) Article 7 does not apply to a pig less than 12 months old provided that it is identified with a temporary mark that—
(a) either by itself or by reference to a document accompanying the pig during the movement, enables the holding from which the pig was last moved to be identified; and
(b) lasts until the pig reaches its destination.
(2) The exception in paragraph (1) does not apply in relation to a pig being moved—
(a) to a market;
(b)to a slaughterhouse;
(c)for the purposes of intra-European Union trade or export; or
(d)in accordance with article 10.
Article 10 refers to shows