Done if by Hand or Hew if by Sword?

[Inziladun]

I think Legate has the right of it.
Obviously those not in Elendil's line had touched it before. The shards of Narsil had been brought to Rivendell after Isildur's death by a 'nobody' esquire. Also, Elven-smiths had reforged it in Rivendell, and you'd think that might involve laying hands on it (unless Aragorn was paranoid enough to want to hold it while they did their thing).

[davem]

http://en.wikipedia.org/wiki/Tyrfing :

The Dwarves made the sword (Tyrfing), and it shone and gleamed like fire. However, in revenge they cursed it so that it would kill a man every time it was drawn and that it would be the cause of three great evils. They finally cursed it so that it would also kill Svafrlami himself.

When Svafrlami heard the curses he tried to slay Dvalin, but the Dwarf disappeared into the rock and the sword was driven deep into the rock missing its victim.

Svafrlami was killed by the berserker Arngrim who took the sword in his turn. After Arngrim, it was worn by Angantyr and his eleven brothers. They were all slain at Samsø, by the Swedish champion Hjalmar, and his Norwegian sworn brother Orvar-Odd; but Hjalmar, being wounded by Tyrfing, has only time to sing his death-song before he dies, and asks Orvar-Odd to bring his body to Ingeborg at Uppsala.

Angantyr's daughter, Hervor (by his wife Tofa) is brought up as a bond-maid, in ignorance of her parentage. When at last she learns it, she arms herself as a shieldmaiden, and goes to Munarvoe in Samsø, in quest of the dwarf-cursed weapon. She finds it and marries Hofund. They have two sons, Heidrek and Angantyr. Hervor secretly gave her son the sword Tyrfing. While Angantyr and Heidrek walked, Heidrek wanted to have a look at the sword. Since he had unsheathed it, the curse the Dwarves had put on the sword made Heidrek kill his brother Angantyr.

Heidrek became king of the Goths. During a voyage, Heidrek camped at the Carpathians (Harvaða fjöllum, cf. Grimm's law). He was accompanied by eight mounted thralls, and when Heidrek slept at night, the thralls broke into his tent and took Tyrfing and slew Heidrek. This was the last one of Tyrfing's three evil deeds. Heidrek's son Angantyr caught the thralls, killed them and reclaimed the magic sword, and the curse had ceased.

All this & a Shieldmaiden too...