/scoreboard objectives add craftedDiamondSword stat.craftItem.276
/scoreboard objectives add usedDiamondSword stat.useItem.276

clear @a[score_usedDiamondSword_min=1] 276

tell @a[score_usedDiamondSword_min=1] Don't use diamond swords!
scoreboard players set @a[score_usedDiamondSword_min=1] usedDiamondSword 0

/scoreboard objectives add hasDiamondSword dummy

scoreboard players add @a hasDiamondSword 1 {Inventory:[{id:"minecraft:diamond_sword"}]}
clear @a[score_hasDiamondSword_min=1] minecraft:diamond_sword

tell @a[score_hasDiamondSword_min=1] Don't use diamond swords!
scoreboard players set @a[score_hasDiamondSword_min=1] hasDiamondSword 0

tell @a {Inventory:[{id:"minecraft:diamond_sword"}]} Don't use diamond swords!

clear @a diamond_sword